Loading machine



July 25, 1944. w. w. SLOANE LOADING MACHINE Original Filed June 25, 1940 2 Sheets-Sheet 1 -w. w. SLOANE 2,354,336

LOADING MACHINE July 25, 1944.

Original Filed June 25, 1940 2 Sheets-Sheet 2 O /04 E 3' I 9 98 9- E29. 81

DOWN 80 NEUTRAL mom 76 1 77 6 75 79 g 68 IV rr'i 77 11 g; 79 89 a 78 90 q I 1 94 78 v f .94 78 78I I 7g 78: 4 TANK I: f I 89 I T/MIr 73 97 T i as 96 77 Ill- 10g n 2 i 97 77 77 I06 77 85 7 I -f I08 I L :L as I06 1' 75' Patented July 25, 1944 UNITED STATES, PATENT OFFICE fmAniit llii caaE' A Goodman Manufacturing Company, Chicago, 111., a corporation of Illinois Original application June 25, 1940, Serial. No.

342,331; Divided and this application April 17;, a 1943, Serial No. 483,441 r '1 Claims. (01. 198-'7) This invention relates to improvements in loading machines, and more particularly relates to an improved fluid pressure operating and controlling system particularly adapted for use with a loading machine of the type operable in confined spaces, such as mines underground.

The principal object of my invention is to provide a new and improved form of loading machine arranged to afford ease and convenience of manipulation and control, particularly with relation towards operation in confined spaces, such as mines.

A more specific object of my invention is to provide a new and improved form of loading machine, so arranged that the elevating conveyer-- may be used for lifting the front end of the machine about the rear track wheels for rerailing the machine and including a novel arrangement whereby the elevating conveyer may float along the ground when loading or when moving along the track wheels during transportation. 1

This application is a division of application a Serial No. 342,331, filed June 25, 1940. r

Other objects of my invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings wherein:

Figure 1 is a fragmentary plan view of alOading machine having one form of fluid pressure actuating and control system constructed in accordance with my invention embodied therein, with certain parts broken awa and certain other parts shown in section;

Figure 2 is a fragmentary view in side elevation of the loading machine shown in Figure 1, with certain parts broken away and certain other parts shown in longitudinal section;

Figures 3 and 4' are detail sectional views of the control valves utilized in the fluid pressure system, showing the valves in different operating positions;

Figure 5 is. a fragmentary detail sectional View showing certain details of one of the control valves; and

Figure 6 is a fragmentary diagrammatic view of a part of the fiuid pressure system, showing the valves in position to permit floating movement of the elevating conveyer. V t

In the drawings a loading machine H! of the trackmounted type is provided; Said loading machine is particularly adapted for gathering and loading coal in mines underground and is constructed along lines somewhat similar to thema chine illustrated in Patent No, 2,201,334, which issued on may 21,, 1940,, to: Frank Cartlidge," so

will not hereinbejshown or described in detail excepting as to the parts thereof which form the basis of my present invention.

The loading machine J0 'ncludesggenerally a track mounted truck having a forwardly projecting elevatingv conveyor 12- pivotallymountedon the forward end thereof, for movement about a horizontal transverse axis spaced above said truck, and for movement about a vertical axis disposed forwardly of the forward: truck wheels.

Gathering elements; I3,-;l3 ofthe usual chain and gathering arm type extend along each sideof the for-ward end of said elevating conveyer and project forwardly of the forwardend thereof.

Areceiving conveyer I4 is disposed beneath the discharge end of said elevating conveyer andis provided with a laterallyswingable discharge end I5, adjustable to dischargematerial to either side I of or directly behind said loadingmachine' The elevating conveyer is transversely pivotedon a swinging frame It, which. is. mounted on the forward end of thetruck H, for movement 1 about a vertical axis. Said elevating conveyer. is vertically movedabout its axis of, horizontal pivotal connection to saidswinging frame by i means of a pair of fluid pressure cylinders l9, l9 having, pistons 20, -20 mounted therein, with piston rods 2|, 2! extensible-therefrom. As herein shown, each of said cylinders is provided'witha rearwardly projecting portion 22 transversely pivoted on the horizontally s wingable frame-l6 by means of a pivotal pin 23. The piston rods 2|, 2| projecting from thecylinders l9, [9 have pivotal connection at their forward ends with the underside of said elevating iconveyer, by

means of pivotal pins 24; 214. A compressionmember 25 is interposed between said frame and 4 the central underportion of said elevatingv conveyer, to cushion said elevating conveyer during vertical adjustment thereof. 1

A fluid pressure cylinder 30, having apiston 3| therein, with a piston rod 32'pr'ojectingfrom said piston, is provided to laterally swing the elevating conveyer l2. Said cylinder is'provided with a rearwardly projecting portion 33, which is pivotally connected with a bracket 34', projecting from the frame for the truck H, by means of a vertically disposed pivotal pin 35. Said piston rod is pivotally connected at its fo'rward'end with a forwardly projecting portion 36. of the hori-' zontally swingable' frame otal pin 3T.

The fluid pressure actuating system for raising or lowering the forward end of the elevatingj conveyer and for swinging it from side to side I6; by means of a pivtype and are each herein shown as being of a well known rotary sliding vane type of pump' Said pumps, as herein shown, are driven from a motor 65 through a chain and sprocket drive 66 in a manner which will nother'einbeshown ,ji

or described since it is no part of my present in-[ vention.

The suction sides of the pumps 'BO and 6| are connected with a fluid storage tank' It by means .the openings 18a, 18a, to and through the central of a pipe 12 and branch pipes 72a and 12b. A

fluid pressure pipe 13 leads from the pressure end. of the pump 60 to a pair of control valves 14 and 15, herein shown as being-open center valves of the piston type and mounted ina single block 68. Said valves are adapted to'control the admission of fluid under pressure to the"had and piston rod ends of the-fluid pressure'cylinderslil, l9, I a

which serve to raise'or'lowerthe elevating conveyer, and to a cylinder which serves to swing said elevating conveyer laterally.

The valves 14 and li' 'arearranged to reverse the direction of flow of fluid in the pipes leading to the cylinders 31] and lfl} l9, respectively, thus permitting one valve to control the admission passageway. Said pipe leads to the exhaust side of a relief valve 82, and the pressure side of a relief valve 83, connected in series with said first mentioned relief valve. The purpose and operation of said relief valves will hereinafter more clearly appear as this specification proceeds.

The passageway 80 is connected with the valves 14 and 15 by means of an end passageway 84 extending transversely of the passageway 80 and an opposite end passageway 85 extending parallel to said first mentioned end passageway.

Fluid under pressure enters the valve 14 ,through the pipe 13. When the two valves ar in a neutral position as shown in Figure 3, fluid under pressure will enters the valve 14 through a port 86 and from said port will pass through in thepistons 17, 11.

and exhaust of fluid to and from the "head and f piston rod ends of the cylinder 30, andpermitting the other valve to control the admission and exhaust of fluid under pressure to and from the piston rod ends ofthe cylinders), IS. The passageways in said valves are also interconnected so that both valves may be operated, simultane- L ously, to facilitate the operation of the loading machine by elevating or lowering the gathering element and at the same time swinging it to one side or the other. The fluid connections between said valves are also so arrangedthat fluid exhausted from one cylinder or pair of cylinders will operate the other cylinder or pair of cylinders, thus simplifying the piping arrangement and the control for operating the pistons in said cylinders.

Referring now in particular to Figures 3, 4 and l 5, and thevalves 14 and 15 said valves are herein shown as being balanced piston valves of the open center type and are each of a'similar con struction, so like part numbers will beapplied to. like parts of each valve, wherever practical. The valve 14 includes a plunger slidablymounted in the block 68 for said valves and having a pair of spaced apart aligned end pistons 11, I1 and an aligned intermediate piston 18 formed inte gral therewith. A valve stem I6 projects from said plunger. The outer pistons 11, TI and the intermediate piston 18 are grooved intermediate their ends. .0penings 11a, 11a lead fromthe grooves in the pistons 11,11 to a passageway 19 extending along th center. of said plunger. The intermediate piston 18 is likewise grooved and the groove'between the lands of said. piston is provided with openings 18a, 18a, leading to the passageway 19.

The block 68 is provided with a passageway 80 which extends parallel to the plungers of the valves 14 and vl5 in the space between said plungers, to connect opposite ends of said valves together.

A pipe 8'| has connection with said passageway 79 and through the openings Ha, Ha From there it will pass through the passageways 84 and 85 to and through theopenings 11a, 11a, in the pistons '11, 1 1 for the valve 15, and out through the openings 16a, 18a of said valve to the tank H, through a pipe '88.

The valve 15 difiers in construction from the valve 14 in that a spring actuated plunger 81 is provided to engage a foot 98 of an operating lever' I04 of said valve, to tend to urge the valve stem 16 of said valve to a down position (see Figure 4). A detent I05 is provided at the lower end of said valve and is adapted to engage a groove I06, to hold said valve in a neutral position against the spring actuated plunger 81. Another groove I08 is adapted to be'engaged by the detent I05, for holding said valve in an extreme down position (see Figure 5).

When the stem of the valve 14 is in an extreme mm down position and the stem of the valve 15 is in 'an extreme up or out position, fluid will enter the valve 14 through the pipe 13 and port 86 (see Figure 4) It will then pass in the space between the intermediate piston 18 and the upper piston 11 and leave said valve through a port 89 and pipe 90 leading to the head end of the cylinder 30. This will horizontally swing the elevating conveyer and gathering mechanism of the loading machine in one direction, in an obvious manner. As fluid enters the head end of said cylinder under pressure, it is exhausted from the piston rod end of said cylinder through a pipe 9|, which leads to a port 92 in the valve 14. From there fluid will pass in the space between the intermediate piston 78 and the lower piston 71 and'through the passageway 85 to and through the central passageway 80. Fluid will pass through the passageway 80 to the end passageway 84 and the valve 15. Fluid will leave said valve through a port 93 and pipe 94. From said pipe, fluid will pass through a reduced return valve 95 to the head ends of the cylinders l9, l9, and elevate the elevating conveyer and gathering and loading element in an obvious manner.

When it is desired to swing the elevating conveyer and gathering mechanism of the machine from side to side, while it is in a fixed position vertically, the valve 15 is in a neutral position. The stem 16 of the valve 14 is then raised to cause fluid to flow through the port 92 and pipe 9| to the piston rod end of the cylinder at and to enter said valve from the'head end of said cylinder through the pipe 90 and port 89, or said stem is moved to the down position shown in Figure 4, to cause a reversal in the flow of fluid through said pipes and valve. Fluid is exhausted were r m a va v a d e ur d t9 he an H r u i h l j .s ev 9 1 155 depe in upon" the position of" saidvalve stern, and through the P w 9 m h Stem im? Va 5 aiiid out through thepipe 138;; p

ii like'manne hen it iss es re leva e l w h fr t d fi l a 'n' were w i e held from lateral movement? thefvalve 14 is in a"neutra1 positionwl'iilfe' the valve' lj" is moved toanup or'down positioiifdependingupon the direction itis desired niove said' elevating conveyer."""Duringtliis operation, the return will be th'rougheither 'Of the pipes 91} ori 'flfi a hd' ollt the-pipe; a v v t I l Thereduced return valve '95 is an ordinary check valve with a by 'pass' 9 5a threinfso arrangedthat fluid under pressure will pass through saidvalveto'the"hea'dendsof the cylinders l9. l9 at a normalr'ate', but when returning will only flow through the restricted lay-pass gasa to retard the flow of fluidin a retui'd'direction 'as' it" is being"exhaustedirom the headendso'f said'cyl inders'; and "decrease the speed "'oflow-erinjg or the elevating'conveyer and resist downward movement ofsaid' elevating conveyerwheh floating on the'groun'd.

Atthes'ame time fluid enters the head ends of thecylinders l9, l9; it l will'heiorced from the piston rod ends of said cylinders through a pipe 96 having connectionwith'a'" port 91 of the valve 15. Fluid will then passin the space between the pistons "18an'd H and out the pipe 8ft to the 1 i; r r .7 i

*If the valve is in the up position shown in Fi'gure'4, fluid will pass to the head ends of. the cylinders l9; H! to raise thefomard en of the elevating conveyer, but if "said valve" is' moved to an extreme down position, fluid'will pass through the passageways'flu and BEthrough th space'h'e tween the lower cylinder l'land'the intermediate cylinder .lfl'and through the port fil and pipe B B-to" the piston rod ends'ofthecylinde'rs l3, l9. At thesarne time'fluicfwill pass'f rofn the head ends'pf said 'cylinders through" the reduced re:

turn valve 95"and'tlie' pipe 9 4'to'thepoitv93 or the"valve 15. Fromsaidport; 'fluid'willpa'ss to the tankll through the'return*pipe"8B.'

The relief valves 82and"83 are connected in the system to relieve pressure upon overload of the cylinders l9," H3 or the'cylinder' or "upon overload ofbo'th 'thecylinder's '19, I 9 ahdftli'e' cylinder 30. The relief valve 82 has connection with the pipe "13 'betv'veen"the ump 68 and the pressure side'of the operating valve'MQ A 99 isprovidedto cennecrse a 'c'onnectio'n'is' provided between th'is'f'pipe and the pipe Blf' leading fro'm'the valves'l'faiid 15, it being noted that said last'lnntioned'pipeis 'orith'e pressure side'ofthevalve 15. Since-the cylinders/l9, 19 are operated through the exhaust side 'of the cylinder filljwheir'all "of said cylinders are operated together, the amount oflpressuiepassingthrough'th ipe 13' must be greaterthan the pressurerequire'd" t'o' operate 1d valves in ser es, and

the cylinder'3fl or the "cylinders 19, It "alone. Y The'reason is that the firstcylinder is operated against"a"back pressure sufficient"to operatethe second cylinde'rii Thus if only one" relief valve were'pro'videdin thes'ysteni','the cylinders it, I!) and the cylinders!) wouldhave to b'eeither oper atedseparateTY or simultaneously, depending upon the pressure at which th'e'relie'f valveis set to "release; it being" obvious "that 'a' relief valve The relief valve 83 Dy-passing pressure from the second cylinder upon overloadf'the fir 'fcylinder'. With the present arr ngement, the relief valve 82is' connected fromthe" pressure line I3 across the'val've' 14;to' the exhaust side of saidvalve.

is connected with the pressure and exhaust sides of the valve 15L: Said relief valves are both balanced. differential pressure valves offaiusual construction. When the cylinde 39 is *bpera'ted" separately and'is overloaded,

"sures on either end of said cylinder will be'relieved through the valve 82 connected between the line 13 and the exhaust side of the pressure j'valve' Hf Overload conditions of the cylinders 19 ,19 will be taken care of by the relief valve 83, connect 'd between the pressure and exhaust of t e'valve 15. When, however, the cyliridefrsjjfi, l9 and the cylinder 33 are operatin simultaneously and are overloaded, fluid under pressure will he released from the line "l3 through the valves 82 and 83'. The relief valve 82 is opened by fluid enteringsaid valve from the pressure pipe 13 and'passing through 'a passageway 68 in said relief valve; to exert a pressure on the lower side of apiston 10p of said valve. In order to prevent opening of said valve when the cylinders I9, 12 and the cylinder 3,0 are operating together under normal load conditions, fluid under pressure is supplied to the end of said piston Hi0 opposite from thepa'slsageway 98 through 'a passa eway l 99a in said'val've, which is connected with the pipe Thishalarrces the'pressure of fluid coir.- ing'fr'om the'pipe I3 and permits-the valve spring to hold said valve in a closed position until the pressure difierential'between the passageways 98 and 99a is sufiicient against'the'valv spring. 'When this differential in pressur isreater "than the pressure of the valve spring, saidr'elief valvewill be n; to release pressure through the pipe99 to; and through the relief valve-83 to the return." There is neappreciab le back pressure on the relief valve 8 sin-co the disc arge si'd of said valve 'is connected directlywith" the return liiie 8'8' said Valve will open whenever the'pressure in the'pip'e 8 l exceeds thepre'ssure at whichsaid valve is set to open.

In Figure 6 the hydraulic fluid pressure acttiat ingdevice's' are show'ninposition to permit the elevating conveyer to floatoii' the rails during transportation, he to follo'wan "uneven hottohi during loading. In order" to permit said elevating 'convyer"to do this, apetc-ock it}? is PIG"- vided. This petcock connects the'pipe 9i; withthe return pipe "88"and' is normally closed, out is opened when it is desired that'the elevating conveyer float along the ground or the rails. When the control valves are in a floating position "the valve 14' is moved to a neutral positi-onand the valve 15 is moved to an extreme down position. When the valve 15 is in this position, theopen petcock I01 will by-pass fluid to'the return pipe 88. A small trickle of fluid, however, passing through the" valve 15 will enter the pipe 96 and the piston rod endsof the cylindersis, Hi.' Th s fluid 'will tend to exert pressure on the piston rod ends of said cylinders and hold the elevating ccnveyer in floating engagement with the ground, the return of fluid froni'the head ends of the cylinders l9, l9 through'thereducejdreturn valve .95 being restricted by therestricted passageway a. to

retard'downward movementof saidelevating'oonveye'r. This maintains" a slight amo nt of fluid pressure'iir'bothf'thhead and" piston rod ends of the cylinders I9,"|9, holding the forward end of said. elevating conveyer'injfloatihg engagement:

to move said piston mil with the ground and'permitting elevation or lowering of said elevating conveyer with respect to the ground as irregularities'are encountered, so

said elevating conveyer may follow ari uneven bottom. The valve I5 is held in a floating posi tion by means of the detent I05 engaging the groove I08.

The cylinders I9, I9 may be, usedtoraise the front wheels of the truck supporting the loading machine, to permit the machine to be readily re-railed at times when it accidentally runs off the track.v In re-railing the machine, the petcock I 01 is closed and the valve is moved to an extreme down position, the valve I4 being in a neutral position. Fluid will thus enter said valve through the passageway 80 and the space between the lower pistons I1, I1 and the intermediate piston 18 and pass through the pipe 96 to the piston rod ends of the cylinders I9,,I9. This will engage the forward end of the gathering and loading element with the ground to lift the front track wheels about the rear track wheels, thus lifting the entire front part of the machine and permitting it to be replaced on the rails. sired, the machine may be swung from side to side when the front track wheels are in a raised If deposition, by means of the cylinder in the hereinbefore described manner. I

When it is desired to hold the front conveyer off of the ground while traveling, the valve 15 is placed in a neutral position when said conveyer reaches the desired position of vertical adjustment, to hold pressure in the head ends of the cylinders I9, IS. The petcock I01 may be either open or closed.

It may be seen from the foregoing that the fluid pressure system is so arranged that the elevating conveyer may be used for lifting the front end of the machine about the rear track wheels to permit the machine to be rerailed, and that said conveyer may also float along the to enter said endof said elevating cylinder, and other means restraining the exhaust of fluid from the other end of said elevating cylinder.

2. In a loading machine, a truck, an elevating conveyer mounted on said truck forlvertical and lateral swinging movement with respect thereto, a fluid pressure cylinderand piston for raising or lowering said elevating conveyer with respect to said truck, another fluid pressure cylinder and piston for swinging said elevating conveyer from side to side, a pump, a tank, a pair of control valves arranged in series for controlling operation of said cylinders and pistons, a pressure pipe leading from said pump to said valves, pressure pipes leading from said valves to the head and piston rod ends of said fluid pressure cylinders, and means permitting said elevating conveyer to float along an uneven bottom including a by pass connection in the pipe leading to one end of the elevating cylinder, to by-pass fluid from said end of said cylinder, but permitting a small trickle of fluid under pressure to enter said end of said elevating cylinder, a valve insaid by-pass line manually operable to open or close'said bypass line, and a reduced return valve in the return from said elevating cylinder, restraining the flow of fluid from the other end of said elevating cylinder.

3. In a loading machine of the class described,

a mobile truck, an inclined elevating conveyer pivoted to said truck for vertical adjustment with respect thereto about its rear end, a double act-- ing fluid pressure cylinder and piston for raising neor lowering the forward end of said elevating conveyer with respect to the ground, a pump for supplying fluid under pressure to said cylinder and piston, a control valve for selectively controlling the admission and release of fluid to the ground during the loading operation or along the rails during transportation, thus providing a readily maneuverable machine operabl in a simple and eflicient mannerand arranged to reduce the hazards of operation underground.

While I have herein shown and described one form in which my invention may be embodied, it will be understood that the construction thereof and the arrangement of the various parts may be altered without departing from the spirit and scope thereof. Furthermore, I do not wish to be construed as limiting my invention to the specific embodiment'illustrated, excepting as it may be limited in the appended claims.

I claim as my invention:

1. In a loading machine, a truck,.an elevating conveyer mounted on said truck for vertical and lateral swinging movement with respect thereto, a fluid pressure cylinder and piston for raising or lowering said elevating conveyer with respect to said truck, another fluid pressure cylinder and piston for swinging said elevating conveyer from sid to side, a pump, a tank, a pair of control valves arranged in series for controlling operation of said cylinders and pistons, a pressure pipe leading from said pump to said valves, pressure pipes leading from said valves to the head and.

head and piston rod ends of said cylinder and piston, and means to cause the forward end of said elevating conveyer to float along an uneven bottom during loading and transportation of the machine including a by-pass valve having connection with one end of said elevating cylinder,

and selectively operable to by-pass fluid from said end of said cylinder, but to permit a small trickle of fluid under pressure to enter said end of said elevating cylinder so as to maintain a yieldable force thereon, to tend to yieldably engage the forward end of said elevating conveyer with the ground.

4. In a loading machine of the class described, a truck, an inclined elevating conveyer transversely pivoted to said truck for vertical adjustment with respect thereto about its rear end, a double acting fluid pressure cylinderfand piston for raising or lowering the forward end of said elevating conveyer about its axis of connection to said truck, a pump for supplying fluid under pressure to said cylinder and piston, a control valve for selectively controlling the admission and release of fluid to the head and piston rod ends of said cylinder and piston, and means to cause the forward end of said elevating conveyer to float along an uneven bottom during loading and transportation of the machine including a by-pass valve having connection with the end of said elevating cylinder which controls the lowering of the forward end of said elevating conveyer, and manually operable to by-pass fluidfrom said end of said cylinder, but to permit a small trickle of fluid under pressure to .enter said end of said elevating cylinder, so as to maintain a p ssu e there n; llIficient to maintain the forward end of said elevating conveyer in yieldable engagement with the ground.

' fluid pressure cylinder and piston for raising or lowering the forward end of said elevating conveyer with respect to the ground, a pump for supplying fluid under pressure to said cylinder and piston, a control valve for selectively controlling the admission and release of fluid to the head and piston rod ends of said cylinder and piston, and means to cause the forward end of said elevating conveyer to float along an uneven bottom during loading and transportation of the machine including a by-pass valve having connection with the end of said elevating cylinder which controls the lowering of the forward end of said elevating conveyer, and manually operable to by-pass fluid from said end of said cylinder, but to permit a small trickle of fluid under pressure to enter said end of said cylinder, so as to react against said yieldable means and maintain the forward end of said elevating conveyer in yieldable engagement with the ground.

6. In a loading machine of the class described, a truck, an inclined elevating conveyer engageable with the ground at its forward end and pivotally mounted on said truck for vertical adjustment with respect thereto about its rear end, a double acting fluid pressure cylinder and piston for raising or lowering the forward end of said elevating conveyer with respect to the ground, a pump for supplying fluid under pressure to said cylinder and piston, a control valve for controlling the admission and release of fluid to the head and piston rod ends of said cylinder and piston, and means to cause the forward end of said elevating conveyer to float along an uneven bottom during loading and transportation of the machine including a by-pass valve having connection with the end of said elevating cylinder which controls the lowering of the forward end of said elevating conveyer, and manually operable to by-pass fluid from said end of said cylinder, but to permit a small trickle of fluid under pressure to enter said end of said elevating cylinder, so as to maintain a slight pressure thereon suifioient to maintain the forward end of said elevating conveyer in yieldable engagement with the ground, and a reduced return valve in the return from the end of said cylinder which supplies pressure to elevate said elevating conveyer, for restraining the flow of fluid from said last mentioned end of said cylinder and maintaining a slight pressure thereon to aid in balancing the pressure on the other end of said cylinder.

7. In a loading machine of the class described, a truck, an inclined elevating conveyer engageable with the ground at its forward end and pivotally mounted on said truck for vertical adjustmeni; with respect thereto about its rear end, yieldable means for cushioning downward movement of said elevating conveyer, a double acting fluid pressure cylinder and piston for raising or lowering the forward end of said elevating conveyer with respect to the ground, a pump for supplying fluid under pressure to said cylinder, 9. control valve for controlling the admission and release of fluid to the head and piston rod ends of said cylinder and piston, and means to cause the forward end of said elevating conveyer to float along an uneven bottom during loading and transportation of the machine including a bypass valve having connection with the end of said elevating cylinder which controls the lowering of the forward end of said elevating conveyer, and manually operable to by-pass fluid from said end of said cylinder, but to permit a small trickle of fluid under pressure to enter said end of said elevating cylinder, so as to react against said yieldable means and maintain the forward end of said elevating conveyer in yieldable engagement with the ground, and a reduced return valve in the return from the end of said cylinder which supplies fluid under pressure to elevate said elevating conveyer, for restraining the flow of fluid from said last mentioned end of said cylinder and maintaining a slight pressure thereon in the direction of the action of said yieldable means.

WILLIAM W. SLOANE. 

